OSCILLATING VERTICAL COOLING CRYSTALLISERS (OVC)

One of the main objectives of the whole sugar technician is the result of extracting the greatest amount of sugar from the massecuite, which is done in two steps:

• Crystallisation by evaporation, followed by
• Cristallisation by cooling

The latter focuses on achieving the continuous crystallization of existing crystals. Since it is the last step of exhaustion in the sugar process manufacture, crystallization by cooling is highly valuable, since an error in the controlled sequence of the process will irreversibly affect the losses of sugar contained in final honey. To achieve this goal, BMA offers the oscillating vertical cooling crystalliser (OVC), with the following advantages:

• Low space requirement thanks to its vertical construction, on the outside of the factory, so that building prices are reduced.
• Possibility of large capacity units. Volume of more than 1,000 t and 1,100 m² of cooling surface.
• Trouble-free handling of high consistency massecuites.
• Uniform relative movement between the massecuite and the cooling elements, achieving an excellent heat transfer between the massecuite and the cooling device.
• Large specific cooling surface, up to 2 m²/m³.
• High level of cooling without formation of fine crystals or inlays.
• Self-cleaning effect that prevents inlays.
• Excellent handling of the residence time and the performance profile on the cooling surface and the water temperature to reach a maximum of crystallisation.
• Cooling system with oscillating elements.

In recent years, this type of cooling crystallisers designed for a flow of 1,000 t has significantly increased its demand worldwide. The success of these crystallisers are based in their matured and improved design where:

• The cooling system consists of a set of cooling elements type coil, through which the flow of water is forced to circulate in counter-current to the massecuite.
• Half of these elements can be connected and disconnected as required by the operating conditions. A low-speed massecuite distributor share out it evenly throughout the entire section.
• The complete cooling system oscillates vertically 1 m; it is this movement and the symmetry of the elements of the cooling system that ensure an optimum spectrum of residence time of the massecuite.
• The vertical movement of the cooling unit can be varied in two steps and is operated by six hydraulic cylinders in a symmetrical arrangement. On the side where the massecuite is, the unit doesn’t require bearings, anti-friction elements or bast-presses.

Other important characteristics are the following:

• Simple, low-cost hydraulic cylinders provide vertical oscillation of the cooling elements. It is not necessary to convert this movement into a circular movement, besides that these cylinders are more accessible and cheaper than the motor-reducers.
• The use of silent pumps with internal gear provide high efficiency and low wear.
• Hydraulic pressure limiting valves prevent overloads.
• Simple incorporation of a water recirculation and cooling system, reducing the consumption of cooling water.
• Low energy consumption.
• The described system also allows the reconditioning of the massecuite at the exit of the crystalliser. This reconditioning is achieved by adding and mixing a small amount of preheated honey with the massecuite, providing a higher temperature with lower viscosity, facilitating its transport and subsequent centrifugation.

The amount of saccharose that can be extracted from the massecuite “C” is directly reflected in the purity of the final honey, so that this type of equipment has a very fast recovery of the investment.

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